I would recommend The Passionate Programmer as the book that is a MUST
The Pragmatic Bookshelf | The Passionate Programmer
I would like to add one more but it is a must for most of the employees.
The Go-Getter: A Story that Tells You How to Be One: Peter B. Kyne: 9781613821695: Amazon.com: Books
A Programmer should have the attitude to go till the end and inculcate the spirit of alternatives and best alternatives. This book brings in that kind of attitude in a story form.
A die hard attitude – not giving up and extensive reading and experimenting habit is required for a Programmer. The above two books put them in the right perspective.